Conventionally, in forming a circuit pattern in a manufacturing process of a semiconductor device, there is employed a photolithography technique wherein a desired pattern is transcribed through a light-exposure, a development processing and the like by using a photoresist. In other words, by applying such a photolithography technique, a mask can be formed by molding a resist film made of a photoresist on a desired pattern and, e.g., a plasma etching can be performed by using the mask, so that recessed/protruded portions of a predetermined pattern are formed in a layer underlying the resist film.
In such a photolithography technique, there is a limit to its spatial resolution due to a relationship between the resolution and a wavelength of light used in the light-exposure, and it is difficult to form in the resist film openings of a dimension less than the limit to the resolution.
To that end, there has been proposed in, e.g., Japanese Patent Laid-open Publication No. 2002-110654 a technique for forming grooves or openings of a width less than the limit to the resolution in the photolithography technique. In such a technique, after forming a resist film by using the photolithography technique, a polymer layer is formed on the entire surface of a substrate by, e.g., CVD. Then, there remains only a polymer layer on a sidewall of the resist film left after performing an anisotropic etching on the polymer layer. Thereafter, an etching process is performed by using a mask having openings whose diameter becomes smaller due to the polymer layer remaining on the sidewall of the resist film, so that there are formed openings such as grooves or holes of a width less than the limit to the resolution in the photolithography technique.
Further, in the photolithography technique, there has also been known a technique using a bottom anti-reflection coating (“BARC”) for preventing a generation of a standing wave due to multi-interference in a resist film. Moreover, there has been proposed in, e.g., WO 03/007357 A1 a technique for forming wirings of a line width narrower than that of the pattern of the initial resist film, by plasma-etching the BARC by using a gas containing CF4 gas and O2 gas to trim transversely the BARC and the resist film.
Among the above-described techniques, by employing the technique wherein the BARC and the resist film are transversely trimmed, it is possible to form wirings of a line width narrower than that of the resist pattern. However, for example, in case openings are formed in an underlying layer by etching, it is impossible to make the diameter of the openings smaller than that of the openings in the resist film.
Further, in the method wherein a polymer layer is formed on the entire surface of a substrate by, e.g., CVD and, then, only the polymer layer remains on a sidewall of the resist film left after performing an anisotropic etching on the polymer layer, there are required the polymer layer forming process, the anisotropic etching process and the like to be performed, so that the number of processes to be performed increases, thereby decreasing the productivity.